Recently, an electrically conductive ink where low temperature sinterability of fine a metal particle, particularly a fine silver particle (for example, Patent Literature 1 (Japanese Patent Laid-Open Application 2013-185213)), and a composition for bonding (for example, Patent Literature 2 (Japanese Patent Laid-Open Application 2004-107728)) have been paid attention.
Accompanying the above matters, the fine silver particles used for the aforementioned objects have been intensively developed, and various fine silver particles and methods thereof have been proposed. For example, in Patent Literature 3 (Japanese Patent Laid-Open Application 2013-142173), there is proposed a method for producing a silver nanoparticle which comprises: preparing an amine mixed liquid that contains an aliphatic hydrocarbon mono-amine (A) having an aliphatic hydrocarbon group and one amino group wherein the aliphatic hydrocarbon group has a total carbon atom of 6 or more, and an aliphatic hydrocarbon mono-amine (B) having an aliphatic hydrocarbon group and one amino group wherein the aliphatic hydrocarbon group has a total carbon atom of 5 or less, and a content of the amine (A) is 5% by mole or more and less than 20% by mole and a content of the amine (B) is more than 80% by mole and 95% by mole or less on the bases of the total moles of the amine (A) and the amine (B); mixing a silver compound and the amine mixed liquid to yield a complex compound containing the silver compound and the amine; and then thermally decomposing the complex compound to form a silver nanoparticle.
According to the producing method of the silver nanoparticle of the above Patent Literature 3, when using the amine mixed liquid containing the aliphatic hydrocarbon mono-amine (A) having 6 or more carbon atoms and the aliphatic hydrocarbon mono-amine (B) having 5 or less carbon atoms, appropriate stabilization of the silver nanoparticle can be obtained.
Further, in Patent Literature 4 (Japanese Patent Laid-Open Application 2014-31542), there is proposed a method for producing a fine silver particle characterized by a first step for mixing a silver compound which can yield a metal silver by thermal decomposition, an alkylamine, at least one alcoholic compound having a solubility to water to yield a complex compound containing the silver compound and the alkylamine, and a second step for thermally decomposing the complex compound to yield a fine silver particle which is covered with a protective film containing the alkylamine.
Though, when using only an alkylamine as the covering molecule for the fine silver particle, it is difficult to yield the complex compound and it takes a long period of time for forming the complex compound, in the method for producing the fine silver particle of the above Patent Literature 4, by adding the alcoholic compound having a solubility to water at the time when the complex compound is prepared by mixing the silver compound which can yield a metal silver by thermal decomposition and the alkylamine, the preparation of the complex compound is accelerated to be able to yield the complex compound efficiently regardless the kind of the alkylamine.